Enzymatic deinking process for office wastepaper with selected noninic surfactants

ABSTRACT

This invention relates to the deinking process for office wastepaper for utilization in a neutral medium. Particularly the invention relates to a deinking process for office wastepaper comprising the steps of: (a) converting wastepaper to pulp; (b) contacting the pulp with a deinking agent comprising of: i) an enzyme active at a pH of from about 4 to about 9 and ii) a nonionic surfactant selected from the group consisting of higher aliphatic alcohol alkoxylates, aliphatic acid alkoxylates, higher aromatic alcohol alkoxylates, fatty acid amides of alkanolamines, fatty acid amide alkoxylates, propylene glycol alkoxylates, block or random copolymers of ethylene and propylene oxide, higher alcohol polyethylene polypropylene block or random adducts and mixtures thereof; in an aqueous medium having a pH of from about 4 to about 9; and (c) removing ink from the pulp by flotation, water washing or a combination of flotation and water washing.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/410,242,filed Mar. 24, 1995, now abandoned, which is a continuation in partapplication of U.S. patent application Ser. No. 08/356,695, filed Dec.15, 1994 now abandoned.

TECHNICAL FIELD

This invention relates generally to the deinking of office wastepaper.In particular, the invention relates to a deinking process for officewastepaper suitable for utilization in a neutral medium.

BACKGROUND OF THE INVENTION

Wastepaper has long served as a source of raw fiber material forpapermaking. It has been standard practice in the art to reclaimwastepaper to allow the reclaimed paper fibers to be used as part or allof the stock of subsequent production of a variety of paper andpaperboard products. Today, greater utilization of reclaimed fiber hasprovided incentive for taking steps to upgrade the reclaimed product.These steps include treatment to effectively remove ink from wastefibers in order to permit their use in the manufacture of newsprint andhigh quality papers. Increasing amounts of office wastepaper arebecoming available with the increased participation by businesses inrecycling. Because of the high quality cellulose fiber in officewastepaper, efficient ink removal is particularly desirable sinceexcellent quality, high value products such as office stationery can beprepared.

In the course of conventional paper reclamation, deinking proceduresinclude steps for converting the wastepaper to pulp and contacting thepulp with an alkaline aqueous deinking medium containing, a chemicaldeinking agent. The physical pulping and the alkalinity of the aqueousmedium cause the partial removal of ink from the pulp fiber. Thedeinking agent completes this removal and produces an aqueous suspensionand/or dispersion of the ink particles. The resulting mixture issubsequently treated to separate the suspended/dispersed ink from thepulp. This separation may be by flotation and/or washing techniquesknown in the art.

Conventional deinking chemicals comprise a complex mixture of chemicals,e.g., sodium hydroxide, sodium silicate, chelating agents, hydrogenperoxide, surfactants, dispersants, collector chemicals andagglomeration chemicals. Generally, including a significant amount ofalkaline material is standard in the art. It is believed that thealkaline material is needed for good saponification and hydrolysis ofthe ink resins as well as enhancement of fiber flexibility. The pH ofthe pulp during the deinking process is usually from about 9.5 to about11. Exposing the cellulosic fibers to this degree of alkalinity tends tocause yellowing of the fibers; so, it is generally necessary to add anoxidative or reductive bleaching agent such as peroxide, formamidinesulfinic acid or sodium hydrosulfite. The use of this complex and highlyalkaline mixture of chemicals is undesirable since the liquor thatresults from the deinking process presents significant environmentaldisposal problems.

There is a need for a method of deinking that operates under slightlyacidic to slightly alkaline or preferably neutral pH conditions andutilizes a simple combination of chemicals. Such a method could resultin waste liquors with significantly reduced disposal problems.Conventional processes have not been particularly successful in specificapplication to xerographically printed and laser printed paper found inoffice wastepaper. The difficulty encountered in the deinking of thesefused toner papers (laser and Xerox produced) has been attributed to thecharacter of the electrostatic ink, specifically to the binder, which isfundamentally different from that used in other printing processes. Forexample, in distinction to the common oil or resin binders of otherinks, the electrostatic ink binder is typically a polymeric material,e.g., polystyrene and polybutadiene, which during the printing processis fixed to the paper by application of pressure and heat. It is theink-fusing action of the copier or laser printer that upon repulpingresults in large, plate-like structures which are typically too large tobe removed by washing or flotation and too flat to be removed by screensand cleaners. The approach that several chemical companies have taken isto chemically modify the surface of the toner flakes such thatagglomeration will occur. The substantially larger particles will thenbe removed by slotted pressure screens and forward centrifugal cleaners.

U.S. Pat. Nos. 5,231,022 and 5,318,905 teach the use of highly alkalinecellulase enzymes for use in the deinking of waste newspaper. The enzymeoptimally operates at a pH of about 9.5 to about 10.5.

Japan Published Application No. 59-9299 teaches a method for deinkingwaste newspaper and magazine print. The method involves the combined useof a surfactant with an enzyme. Cellulase enzymes are suggested for use,particularly those which operate effectively under basic pH conditions(i.e., pH of 8.0 to 11.5). The reference does not disclose nor suggestthat its teachings can be utilized for deinking mixed office waste,which utilizes inks and print processing conditions that far differ fromthose used in newsprint and magazine print.

Despite the above teachings, there exists a clear need in the art for amethod which effectively functions to deink mixed office waste and isoperative at slightly acidic to slightly neutral pH aqueousenvironments.

BRIEF SUMMARY OF THE INVENTION

Surprisingly a deinking agent has been discovered which is suitable foruse in a medium having a pH of from slightly acidic (about 4) toslightly alkaline (about 9), or preferably neutral medium. The deinkingagent is effective in the treatment of office wastepaper by providingreclaimed pulp fiber having a high degree of dirt removal and goodbrightness. A process for deinking office wastepaper utilizing thedeinking agent has been discovered which provides excellent ink and dirtremoval as well as good brightness. The deinking agent can also beutilized in a conventional flotation deinking system and/or washingdeinking system with little or no modification. Further, a complexmixture of chemicals is unnecessary when utilizing the deinking processand deinking agent of the present invention.

The present invention relates to a deinking process for officewastepaper comprising the steps of:

a) converting wastepaper to pulp;

b) contacting the pulp with a deinking agent comprising:

i) an enzyme active at a pH of from about 4 to about 9; and

ii) a nonionic surfactant selected from the group consisting of higheraliphatic alcohol alkoxylates, aliphatic acid alkoxylates, higheraromatic alcohol alkoxylates, fatty acid amides of alkanolamines, fattyacid amide alkoxylates, propylene glycol alkoxylates, block or randomcopolymers of ethylene and propylene oxide, higher alcohol polyethylenepolypropylene block or random adducts and mixtures thereof;

in an aqueous median having a pH of from about 4 to about 9; and

c) removing ink from the pulp by flotation, water washing or acombination of flotation and water washing.

It Is an object of the present invention to provide a process fordeinking office wastepaper.

It is an additional object of the present invention to provide a noveldeinking agent.

These and other objects will be appreciated by those skilled in the artas reference is made to the Drawings and Detailed Description of thePreferred Embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the method used in Example XI.

FIGS. 2 and 3 are comparison graphs of results obtained when usingInkmaster™ 750 alone versus a combination of Inkmaster™ 750 and SP342 asthe respective deinking agents.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In describing the preferred embodiment, certain terminology will beutilized for the sake of clarity. Such terminology is intended toencompass the recited embodiment, as well as all technical equivalentswhich operate in a similar manner for a similar purpose to achieve asimilar result.

(a) Definitions

"Alkyl" means a carbon-containing chain which can be straight, branchedor cyclic, substituted (mono- or poly-) or unsubstituted; and saturatedor unsaturated.

"Enzyme" comprises multi-enzyme complexes and mixtures of enzymes.

"Fatty alcohol(s)" comprises primary, secondary and tertiary,straight-chain or branched alcohols, preferably primary, straight-chainalcohols having between about 8 and about 30 carbon atoms. Alcoholssuitable for use include coconut fatty alcohols, tallow fatty alcohols,animal tallow fatty alcohols and mixtures thereof. Also, stearyl fattyalcohols, oleyl fatty alcohols, palmityl fatty alcohols and arachidylfatty alcohols can be used individually or in blends. They can beprepared synthetically or can be derived from natural oils. Preferredfor use are straight-chain primary alcohols with from about C₈ to aboutC₂₂ alkyl groups.

"Office wastepaper" means used papers comprising xerographically printedand laser printed paper preferably comprising a majority (generallygreater than about 70%) and more preferably comprising allxerographically printed or laser printed paper.

All percentages and ratios given are on a weight basis unless otherwiseindicated.

(b) The Invention

The deinking agent for use in the deinking method of the presentinvention comprises an enzyme having activity, preferably optimalactivity, at a pH range of from slightly acidic (about 4) to slightlyalkaline (about 9) and a nonionic surfactant.

An enzyme suitable for use is active (in an aqueous medium) at a pH ofgenerally from about 4 to about 9, preferably from about 4 to about 8,more preferably from about 5.5 to about 7.5, even more preferably fromabout 6 to about 7 and most preferably from about 6.5 to about 7. Theenzyme is characterized by its ability to modify and/or breakdowncellulosic or cellulose-bonded matter.

Examples of suitable enzymes include cellulase derived from animals,plants, bacteria and fungi such as those produced by the fungi,Aspergillus niger, Trichoderma virde and Thielatia terrestris, Humicolaand Bacillus. Preferred enzymes for use are cellulase enzymes.Multi-enzyme complexes that are substantially cellulases are alsopreferred.

Commercially marketed products preferred for use include:

a) DENIMAX™ (CAS Number and name: 9012-54-8, cellulase), produced byNOVO NORDISK BIOINDUSTRIALS, INC., which is a stabilized liquidendo-glucanase obtained by submerged fermentation of a non-pathogenicmold having an activity of about 100 EGLU/ml (approximately 80 cmu/g asdetermined by Novo Assay method, AF275) and a pH range of from about 3.8to about 8 and an optimal pH of from about 6 to about 8; and

b) SP342™, (CAS number and name: 9012-54-8, cellulase), produced by NOVONORDISK BIOINDUSTRIALS, INC., which is a multi-enzyme complex, a mixtureof cellulases and hemicellulases where cellulases comprise the majorityof the catalytic activity. The complex is active within a pH range offrom about 3.8 to about 8.

Preferred enzymes for use have little or no endocellulase activity (lessthan or equal to about 0.01 μg/g) as measured by Avicellase assay. Thisassay is standard in the art and is a measure of activity towards aninsoluble cellulose substrate, where the activity is an expression ofthe amount of cellulose solubilzing power. The limit of detection isapproximately about 0.001 μg/g.

Nonionic surfactants suitable for use are higher (greater than C₈)aliphatic alcohol alkoxylates, aliphatic acid alkoxylates, higheraromatic alcohol alkoxylates, fatty acid amides of alkanolamines, fattyacid amide alkoxylates, propylene glycol alkoxylates, block or randomcopolymers of ethylene and propylene oxide, higher (greater than C₈)alcohol polyethylene polypropylene block or random adducts and mixturesthereof.

Preferred nonionic surfactants are selected from the group consistingof:

1) a fatty alcohol having a carbon number of from about 8 to about 22,alkoxylated with ethylene oxide and propylene oxide, as represented byformula (I)

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H(I);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to 22; x represents the number of oxyethylenegroups per molecule and is in the range of from about 3 to about 25; andy represents the number of oxypropylene groups per molecule and is inthe range of from about 1 to about 10. Examples of commerciallyavailable products are sold under the lnkMaster™ and Antarox® trademarksby Rhone-Poulenc Inc.;

2) a fatty alcohol having a carbon number of from about 8 to about 22,alkoxylated with ethylene oxide and propylene oxide, as represented byformula (II):

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --(CH.sub.2 CH.sub.2 O).sub.x' --(CH.sub.2 CH(CH.sub.3)--O).sub.y' --H(II);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22; x and x', which may be the same ordifferent, represents the number of oxyethylene groups per molecule andis in the range of from about 2 to about 25; and y and y', which may bethe same or different represents the number of oxypropylene groups permolecule and is in the range of from 0 to about 10 . Examples ofcommercially available products are sold under the InkMaster™ trademarkby Rhone-Poulenc Inc.;

3) a fatty acid having a carbon number of from about 8 to about 22,alkoxylated with ethylene oxide and propylene oxide, as represented byformula (III):

    R--C(O)O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H(III);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22; x represents the number ofoxyethylene groups per molecule and is in the range of from about 3 toabout 25; and y represents the number of oxypropylene groups permolecule and is in the range of from about 2 to about 15. Examples ofcommercially available products are Lionsurf®, Nonatell®, Hipochem®, andBerocell® products sold respectively by Lion Industries, Inc., Shell OilCompany, High Point Chemical Corp. and EKA Nobel AB;

4) an aromatic alcohol such as phenol having alkyl chain(s) with acarbon number of from about 8 to about 20, alkoxylated with ethyleneoxide, as represented by formula (IV): ##STR1## wherein R and R'independently are H or an alkyl group which is branched orstraight-chain having a carbon number of from about 8 to about 14; and xis the number of oxyethylene groups per molecule and is in the range offrom about 1 to about 20. Examples of commercially available productsare InkMaster™, Igepal®, and Alkasurf®, products sold by Rhone-PoulencInc.;

5) fatty amide of alkanolamide of formula (V): ##STR2## wherein R' andR" may be the same or different and are H or CH₂ CH₂ OH or CH₂CH(CH₃)--OH and R is a fatty alkyl group having a carbon number of fromabout 8 to about 20. Examples of commercially available products areAlkamide® products sold by Rhone-Poulenc Inc.;

6) an alkoxylated fatty acid amide of alkanolamide of formula (VI):##STR3## wherein R is a fatty alkyl group having a carbon number of fromabout 8 to about 20; and x represents the number of oxyethylene groupsper molecule and is in the range of from about 2 to about 10. Examplesof commercially available products are Alkamide® products sold byRhone-Poulenc Inc.;

7) a propylene glycol alkoxylate of formula (VII):

    HO--(CH.sub.2 CH.sub.2 O).sub.o (CH.sub.2 CH(CH.sub.3)--O).sub.m (CH.sub.2 CH.sub.2 O).sub.p --H                                     (VII)

wherein o and p are the number of oxyethylene groups per molecule andare in the range of from about 3 to about 15 and m is the number ofoxypropylene groups per molecule and is in the range of from about 25 toabout 40 . Examples of commercially available products are Antarox®products sold by Rhone-Poulenc Inc. and products having a CTFAdesignation of Poloxamer;

8) a block or random copolymer of ethylene and propylene oxide offormula (VII):

    HO(CH(CH.sub.3)CH.sub.2 O).sub.m (CH.sub.2 CH.sub.2 O).sub.p (CH(CH.sub.3)CH.sub.2 O).sub.n H                          (VIII)

wherein m and n are the number of oxypropylene groups per molecule andare in the range of from about 10 to about 25 and p is the number ofoxyethylene groups per molecule and is in the range of from about 5 toabout 25. Examples of commercially available products are Antarox®products sold by Rhone-Poulenc Inc. and products having a CTFAdesignation of Meroxopol;

9) an ethoxylated fatty acid glycol and/or polyethylene glycol esters offormula (IX):

    R--C(O)O--(CH.sub.2 CH.sub.2 O).sub.x --R.sup.1            (IX)

wherein R is a fatty alcohol of greater than C₈ ; R¹ is alkyl of greaterthan C₈ or H; and x represents the number of oxyethylene groups permolecule and is in the range of from about 5 to about 200. Examples ofcommercially available products are Alkamus® products sold byRhone-Poulenc Inc. and products having a PEG castor oil CTFAdesignation; and

10) an ethoxylated fatty alcohol of formula (X):

    RO(CH.sub.2 CH.sub.2 O).sub.x --H                          (X)

wherein R is a fatty alcohol; and x represents the number of oxyethylenegroups per molecule and is in the range of from about 1 to about 20.Examples of commercially available products are Rhodasurf® products soldby Rhone-Poulenc Inc.

Of the above classes of nonionic surfactants, while not wishing to bebound to any particular theory, it is believed that the surfactants ofclass 8 may not perform as well as those of the other classes.

More preferred nonionic surfactants within the above classes include:

1) Those of Formula (I) wherein R is a straight-chain or branched alkylgroup having a carbon number of from about 16 to 20, x represents thenumber of oxyethylene groups per molecule and is in the range of fromabout 10 to about 20, and y represents the number of oxypropylene groupsper molecule and is in the range of from about 4 to about 8. Acommerical example of such a nonionic surfactant is InkMaster™ 750; orwherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to 14, x represents the number of oxyethylenegroups per molecule and is in the range of from about 3 to about 12, andy represents the number of oxypropylene groups per molecule and is inthe range of from about 1 to about 6. A commercial example of such anonionic surfactant is Antarox® LA-EP-16, sold by Rhone-Poulenc;

2) Those of Formula (II) wherein R is a straight-chain or branched alkylgroup having a carbon number of from about 16 to about 20, x and x'represents the number of oxyethylene groups per molecule and is in therange of from about 4 to about 10, and y and y' represents the number ofoxypropylene groups per molecule and is in the range of from about 1 toabout 5;

3) Those of Formula (III) wherein R is a straight-chain or branchedalkyl group having a carbon number of from about 12 to about 18, xrepresents the number of oxyethylene groups per molecule and is in therange of from about 3 to about 25, and y represents the number ofoxypropylene groups per molecule and is in the range of from about 2 toabout 15. A commercial example of such a nonionic surfactant isHipochem® DI600, sold by High Point Chemicals;

4) Those of Formula (IV) wherein R and R' is H or a branched orstraight-chain having a carbon number of from about 8 to about 14 and xis the number of oxyethylene groups per molecule and is in the range offrom about 8 to about 12. A commerical example of such a nonionicsurfactant is lnkMaster™ 730;

5) Those of Formula (V) wherein R' and R" are H or CH₂ CH₂ OH or CH₂CH(CH₃)--OH and R is a fatty alkyl group having a carbon number of fromabout 8 to about 14;

6) Those of Formula (VI) wherein R is a fatty alkyl group having acarbon number of from about 8 to about 14 and x represents the number ofoxyethylene groups per molecule and is in the range of from about 4 toabout 8;

7) Those of Formula (IX) wherein R is a fatty alcohol of greater than C₈; R¹ is alkyl of greater than C₈ or H; and x represents the number ofoxyethylene groups per molecule and is in the range of from about 8 toabout 30; and

8) Those of Formula (X) wherein R is a fatty alcohol having a carbonnumber from about 12 to about 18, and x represents the number ofoxyethylene groups per molecule and is in the range of from about 5 toabout 15. A commercial example of such a nonionic surfactant isRhodasurf® BC720, sold by Rhone-Poulenc Inc.

Of the above, the use of the following classes of nonionic surfactantsis particularly suggested: those of Formula (I), (II), (III), (IV), (V),(VI) and (X) as defined above.

The deinking agent is to be applied to wastepaper which is in the formof a pulp, that is, to wastepaper which has first been substantiallyreduced to individual fibers. Thus the first step in the process of thepresent invention is to convert wastepaper to a pulp. Pulping can beconducted using any of the various conventional processes and equipmentdesigned for this purpose. Most conveniently, the wastepaper processfeedstock is treated in a device known as a "hydrapulper," whichproduces a slurry of the fibers in water. Preferably the pulping isconducted in a neutral medium. Most preferably, it is conducted withoutthe use of chemical additives, i.e., with only the use of water.

After the pulping step, the resulting fibers are contacted in an aqueousmedium with the deinking agent. This contact step can suitably beconducted in the pulping equipment, for instance, by simply adding thedeinking agent to the aqueous slurry of the equipment used to pulp thewastepaper, e.g., hyrdrapulper. Alternatively, the contact may becarried out using separate processing equipment which provides foragitation and temperature control of the aqueous pulp slurry.

For the contact step, a sufficient amount of enzyme is utilized toachieve an efficient diffusion rate such that substantially all of thepulp fiber ((generally greater than about 70%, preferably greater thanabout 80% and most preferably greater than about 90%) comes into contactwith the enzyme component. Determining a sufficient amount is within theskill of an artisan. The amount of enzyme is generally in the range offrom about 0.007% to about 0.056%, preferably from about 0.018% to about0.029%, and most preferably from about 0.020% to about 0.027%, by weightof the pulp slurry.

A sufficient amount of nonionic surfactant is utilized to achieveappropriate interaction with the enzyme to achieve the synergisticeffect. Determining a sufficient amount is within the skill of anartisan. Generally, the range is from about 0.02% to about 0.25%,preferably from about 0.035% to about 0.1% and most preferably fromabout 0.04% to about 0.075%, by weight of the pulp slurry.

The efficiency of the deinking agent can be significantly influenced bythe pH of the pulp slurry during the contact step. Fluctuations in thepH can result in deactivation of the enzyme component of the deinkingagent. During addition of the deinking agent and the activation periodthe pulp slurry can have a pH ranging from about 4 to about 9,preferably about 4 to about 8, more preferably from about 5.5 to about7.5 , even more preferably from about 6 to about 7, and most preferablyfrom about 6.5 to about 7. A neutral pH is preferred. The pulp slurry pHis to be consistent with the activity pH range of the enzyme, preferablythe optimal activity pH range of the enzyme. The incorporation ofbuffering materials such as sodium citrate or sodium phosphate tomaintain an appropriate pH is preferred.

It is important to maintain an appropriate pulp slurry temperatureduring the contact step. The temperature is to be consistent with theactivity temperature range, preferably the optimal activity temperaturerange, for the enzyme component of the deinking agent. Fluctuations intemperature can deactivate/denature the enzyme component. Determiningthe appropriate temperature range is within the skill of an artisan.Generally the range is from about 40° C. to about 65° C., preferablyfrom about 45° C. to about 60° C. and most preferably from about 52° C.to about 58° C.

The activation period for the deinking agent is the time needed to allowsubstantially all of the paper fibers in the pulp slurry to come intocontact with the deinking agent. Conditions such as the degree ofdilution of the pulp slurry and the utilization of agitation can effectthe amount of time needed. The determination of the appropriate amountof time needed is within the skill of an artisan. Generally, theactivation period can range from about 5 to about 90, preferably fromabout 10 to about 60 and most preferably from about 15 to about 30minutes.

The enzyme and nonionic surfactant components of the deinking agent areprepared by conventional means. The enzyme and nonionic surfactant canbe combined by mixing prior to addition to the pulped wastepaperslurried in water or the components can be added and mixed into theslurry in any order of addition.

In addition to water, pulp and deinking agent, the contact slurry mayfurther comprise substances conventionally employed in deinkingprocesses, e.g., brighteners, solvents, antifoam agents and watersofteners. The use of additional deinking agents is neither necessarynor preferred.

The overall deinking process generally comprises pulping or macerationof the wastepaper and ink removal by a flotation system, a water washingsystem or a combination flotation/water washing system. A screening orcoarse cleaning stage or stages can be utilized to remove contaminantssuch as glass, stone, metal and staples. A centrifugal cleaning stage orstages can be utilized to remove light weight materials such asplastics. Typical deinking processes are described in Fergusen, L. D.,"Deinking Chemistry: part 1" July 1992 TAPPI Journal pp. 75 to 83;Ferguson, L. D., "Deinking Chemistry: part 2" August 1992 TAPPI Journalpp. 49-58; and Spielbauer, J. L. "Deinking System Overview", Voith, Inc.Appleton, Wis., pp. 1-9. To the extent necessary for completion, thesereferences are expressly incorporated herein by reference.

The preferred deinking process of the present invention comprises thesteps of (a) converting the wastepaper to a pulp (preferably whenutilizing an aqueous medium having from about 10% to about 14% by weightpulp on a dry weight basis); (b) contacting the pulp with a sufficientamount of the deinking agent as defined above in an aqueous mediumhaving a pH of from about 4 to about 9; and (c) removing ink (which issuspended or dispersed) from the pulp by flotation, water-washing, or acombination of flotation and water washing.

During the contacting step, the pulp slurry generally can comprise fromabout 1.0% to about 6.0%, preferably from about 1.5% to about 5.5%, morepreferably from about 2.5% to about 4.5% and most preferably from about3.2% to about 3.8% pulp on a dry weight basis. Before addition, the pulpslurry's pH and temperature should be checked and, if needed, adjustedsuch that the pH and temperature of the slurry is within the activityranges for pH and temperature (preferably within the optimal activityranges) of the enzyme component of the deinking agent. Preferably afterthe deinking agent has been added to the pulp slurry and an adequateactivation period has been completed, the pH and/or temperature areadjusted via conventional means, e.g., the addition of buffers oraddition of heat, for a sufficient period of time to denature the enzymecomponent of the deinking agent. Preferably the pH and/or temperatureare raised to about 9 for pH and/or about 55° C. for the temperature todenature the enzyme component. Increasing the pH beyond 9 can causealkaline darkening and should be avoided.

As previously indicated, the deinking agent of the present invention canbe included in the aqueous liquor (e.g., water) into which thewastepaper is initially pulped; into the aqueous pulp produced after thewastepaper is pulped; or into the flotation cell. Preferably, thedeinking agent is incorporated after the wastepaper has been pulped.

The deinking can be conducted in the presence of additional chemicalshowever it is preferred that the chemicals used consist essentially ofthe deinking agent, buffers and optionally additional surfactants to aidin the flotation and/or washing steps. Peroxide can be included ifdesired, however an advantage of the invention is that it is usuallyunnecessary and is therefore not preferred.

The invention is further defined by the following non-limiting examples.

EXAMPLE I

The following is an example of a laboratory scale deinking process inwhich xerographically printed paper is recycled using the deinking agentof present invention:

Sample Preparation

To provide a uniform ink concentration in the pulper, a sheet of paperwith a known ink concentration is xerographically reproduced multipletimes. The identical sheets are then twice passed through a mechanicalpaper shredder.

Hydrapulping

Hot tap water (50°-54° C.) is added to a Formax™ 1800H Adirondackhydrapulper. The xerographic paper is then added to reach a pulpconsistency of 14% of pulp fiber by weight of the total aqueous medium.Pulping is conducted at ambient pH (about 9) until the xerographic paperis thoroughly defibered (about 15 minutes).

Intermediate Reactor

After pulping, a large sample is diluted to about 3.5% by weight pulpconsistency and added to a two liter jacketed reactor. The pH isadjusted to about 6.5 using a 10% solution of H₂ SO₄. The temperature ofthe pulp slurry is raised to about 55° C. At a point of uniform mixingand constant pH and temperature, 0.2% by weight lnkMaster™ 750, and 190ml/ton Novo Nordisk enzyme SP342 on a dry fiber weight basis are addedand well mixed at a constant rate for about 20 minutes. After mixing,the pH is adjusted to 9 with a 15.2% NaOH solution to denature theenzyme.

Flotation Deinking

The pulp is diluted to about 1% by weight by taking 1429 g of about 3.5%consistency pulp and diluting with hot tap water to a final volume ofabout five liters. The 1% slurry is then added to a Denver FlotationCell, Model D-1, having a five liter capacity. The pH is then adjustedto about 8.8-9.2 with NaOH. InkMaster™ 750, a nonionic surfactantfalling within the scope of Formula (I) at about 0. 2% (by weight) isadded to the float cell and premixed for about two minutes at anagitation rate of about 2100 rpm. Air is introduced at three liters perminute and continued at that rate for about three minutes. The floatrejects are collected from the cell by skimming the foam along the planeof a weir in a consistent manor. The rejects are saved for yieldcalculations. The slurry remaining in the float cell is mixed for about30 seconds with no air and used as the float accepts.

Sampling Points

A sample for Canadian Standard Freeness measurement is taken at the endof the intermediate reactor mixing time. Samples for handsheetpreparation are taken after intermediate reactor mixing (float feedsample) and after flotation (float accepts sample). Triplicate sheetsare prepared from each sample and are analyzed for dirt count. Two ofthe three handsheets prepared are then analyzed for brightness. Theremaining sheet is used to measure tensile strength.

Handsheet Preparation

The handsheets are made using a TAPPI Standard 159 mm diameter sheetformer with stirrer, a TAPPI standard couch roll, and a TAPPI standardcouch plate as described in TAPPI Test Method T 205 om-88. This testmethod is followed with the following exceptions. The paper is defiberedand prepared using the above procedure. The handsheets are pressed usinga standard pneumatic press with gauge for about 1.5 minutes at about 50psi. The sheets are dried in ring stacks overnight under constanttemperature and constant humidity conditions.

Testing

Canadian Standard Freeness testing is conducted Following TAPPI Method T228 os-58. Brightness testing is performed in duplicate using theTechnidyne Handybright brightness meter (based on percent lightreflectance at about 457 nm). Each handsheet is cut into seven equal pieshaped slices then stacked on top of each other with the wire side up.The central portion of the top slice is measured and then placed at thebottom of the stack. The next slice is measured until all slices aremeasured. The final brightness value for each sample is determined byaveraging 14 values (two sheets per sample or seven values per sheet).The standard deviation of the 14 values is typically in the range offrom about 0.30 to about 0.75.

The handsheets are evaluated for ink content using an image analysissystem. Fifty random fields having an area of approximately 35 mm² perfield are evaluated per sheet so that the total area assessed is about1750 mm² per sheet. Analysis is conducted using a Leco 2001 ImageAnalysis System. Dirt count, in parts per million, is determined forparticles larger than about 0.0025 mm².

The handsheets are evaluated for strength properties using TAPPIStandard Test Method T494 om-88, "Tensile Breaking properties of Paperand Paperboard" with some modifications. Handsheets are kept in aconstant temperature and humidity chamber until testing. Then, eachsheet is cut into seven strips measuring about 15 mm×110 mm. Each stripis then evaluated using an Instron Tensile Strength testing machine andan average tensile index is determined.

The results of these tests are presented in Table I.

EXAMPLE II

The procedure of Example I is repeated with the exception that no enzymeor surfactant is added to the intermediate reactor. This provides acontrol experiment for the experiments involving the SP342 enzyme. Theresults are presented in Table I.

EXAMPLE III

The procedure of Example I is repeated with the exception that about 63ml/ton of SP342 is added to the intermediate reactor. No surfactant isadded to the intermediate reactor. The results are presented in Table I.

EXAMPLE IV

The procedure of Example I is repeated with the exception that about 190ml/ton SP342 is added to the intermediate reactor. No surfactant isadded to the intermediate reactor. The results are presented in Table I.

EXAMPLE V

The procedure of Example I is repeated with the exception that about 450ml/ton SP342 is added to the intermediate reactor. No surfactant isadded to the intermediate reactor. The results are presented in Table I.

EXAMPLE VI

The procedure of Example I is repeated with the exception that the pH inthe intermediate reactor is adjusted to about 7.0 and Denimax L at about253 ml/ton is substituted as the added enzyme. InkMaster™ 750 is addedat about 0.2% to the intermediate reactor as well. The results arepresented in Table I.

EXAMPLE VII

The procedure of Example I is repeated with the exception that the pH inthe intermediate reactor is adjusted to about 7.0 and no surfactant orenzyme is added. This provides a control run for the experimentsinvolving Denimax L enzyme. The results are presented in Table I.

EXAMPLE VIII

The procedure of Example I is repeated with the exception that the pH inthe intermediate reactor is adjusted to about 7.0 and about 63 ml/tonDenimax L is added. No surfactant is added to the intermediate reactor.The results are presented in Table I.

EXAMPLE IX

The procedure of Example I is repeated with the exception that the pH inthe intermediate reactor is adjusted to about 7.0 and about 253 ml/tonDenimax L is added. No surfactant is added to the intermediate reactor.The results are presented in Table I.

EXAMPLE X

The procedure of Example I is repeated with the exception that the pH inthe intermediate reactor is adjusted to about 7.0 and about 450 ml/tonDenimax L is added. No surfactant is added to the intermediate reactor.The results are presented in Table I.

EXAMPLE XI

The following is an example of a pilot scale deinking process of thepresent invention: A pilot scale trial is conducted using Novo Nordiskenzyme SP342 with InkMaster™ 750 vs. a control (no enzyme; InkMaster™750 only) to determine if enhanced dirt removal, as observed in the lab,can be achieved on this scale. The experiments involve repulping mixedoffice wastepaper (MOW)) with about 70% xerographic content at about 10%pulp consistency for about 30 minutes at ambient pH (about 7.88) and ata temperature of about 50° C. The stock is then diluted to about 3.5%pulp consistency and the pH and temperature are adjusted to about 6.5and about 55° C. respectively. At this point, about 2 lb/ton InkMaster™750 is added for the control run (Example I) and about 2 lb/tonInkMaster™ 750 plus 190 ml/ton SP342 is added for the enzyme run(Example II). This slurry is allowed to mix for about 20 minutes in eachexperiment. The slurry is then reduced to about 1% pulp consistency andan additional 1 lb/ton InkMaster™ 750 is added and mixed prior toflotation. The stock is then cycled for 6 passes through a Voithdeinking flotation cell. After 6 passes, the float accepts are thickenedon a sidehill screen. Brightness pads are made from samples taken atfloat cell feed, float cell accepts at half and full-time, and sidehillscreen accepts. Brightness measurements are made in triplicate andindicate a two point gain with enzyme vs. the Control. Canadian StandardFreeness is measured in duplicate at the float cell feed following the3.5% consistency step. The values are equivalent for both runs at 356ml. Handsheets are made from the same stock as brightness pads for dirtcount determination (five sheets/sample). Dirt counts are measured andpercent dirt removal vs. process stage is evaluated. The run usingenzyme plus surfactant treatment shows a 26% increase in dirt removalvs. the control for both half-time float accept and full-time floataccept stages. A 31% increase in dirt removal is observed with enzymetreatment vs. the control at the side-hill accept stage. The results ofthese tests are presented in Table I, and are illustrated in FIGS. 1-3.

                                      TABLE I                                     __________________________________________________________________________                       LABORATORY DEINKING RESULTS                                EXAMPLE NO.        I        II       III      IV       V                      __________________________________________________________________________    Enzyme             SP342,   Control  SP342,   SP342,   SP342,                                    190 mL/ton        63 mL/ton                                                                              190 mL/ton                                                                             450 mL/Tton            Surfactant         InkMaster ™ 750                                         Dirt Removal (%)   99.1     92.0     95.1     95.7     91.9                   Process Brightness Gain                                                                          8        6.7      8.4      8        7.5                    Freeness (ml.)     335      300      326      312      356                    Mean Tenslle Index (N-M/g)                                                                       29.1     28       30.4     28.9     30.9                   Δ Dirt Removal vs. Control                                                                 7.1               3.1      3.7      -0.1                   Δ Brightness Gain vs. Control                                                              1.3               1.7      1.3      0.8                    Δ Freeness vs. Control                                                                     35                26       12       56                     Δ Mean Tenslle Index vs. Control                                                           1.1               2.4      0.8      2.9                    __________________________________________________________________________    EXAMPLE NO.        VI       VII      VIII     IX       X                      __________________________________________________________________________    Enzyme             Denimax L,                                                                             Control  Denimax L,                                                                             Denimax L,                                                                             Denimax L,                                253 mL/ton        63 mL/ton                                                                              253 mL/ton                                                                             450 mL/ton             Surfactant         InkMaster ™ 750                                         Dirt Removal (%)   98.8     95.1     97.2     97.4     96.9                   Process Brightness Gain                                                                          7.7      8.4      9.5      9.3      9.2                    Freeness (ml.)     312      321      312      307      326                    Mean Tenslle Index (N-M/g)                                                                       28.9     29.4     31       30.4     30.2                   Δ Dirt Removal vs. Control                                                                 3.7               2.1      2.3      1.8                    Δ Brightness Gain vs. Control                                                              -0.7              1.1      0.9      0.8                    Δ Freeness vs. Control                                                                     -9                -9       -14      5                      Δ Mean Tenslle Index vs. Control                                                           -0.5              1.6      1        0.8                    __________________________________________________________________________                       PILOT SCALE DEINKING RESULTS                               EXAMPLE NO.        XI                                                         __________________________________________________________________________    Enzyme             Control  SP342,                                                                        190 mL/ton                                        Surfactant         InkMaster ™                                                                         InkMaster ™                                                       750, 2 lb/ton                                                                          750, 2 lb/ton                                     Half-time Dirt Removal (%) vs. Float Feed                                                        49.6     62.6                                              Full-time Dirt Removal (%) vs. Float Feed                                                        64.2     80.8                                              Half-time Brightness Gain vs. Float Feed                                                         4.6      6.5                                               Full-time Brightness Gain vs. Float Feed                                                         6.2      8.1                                               Avg. Freeness (mL) 356      356                                               __________________________________________________________________________

EXAMPLE XII

The procedure of Example I is repeated with the exceptions that theintermediate reactor and float cell volumes are increased to 4 liter and12 liter respectively, that 0.05% InkMaster™ 730 is used in theintermediate reactor and flotation steps and that sampling points are at0.5 minute intervals during flotation and that only ink removal by dirtcount measurement is assessed. Ink removal results are presented inTable II.

EXAMPLE XIII

The procedure of Example XII is repeated with the exceptions that noenzyme is added to the intermediate reactor, thereby, providing acontrol experiment. Ink removal results are presented in Table II.

EXAMPLE XIV

The procedure of Example I is repeated with the exceptions that theintermediate reactor and float cell volumes are increased to 4 liter and12 liter respectively, that 0.025% Alkamide® DC-212/S is used in theintermediate reactor and flotation steps and that sampling points are at0.5 minute intervals during flotation and that only ink removal by dirtcount measurement is assessed. Ink removal results are presented inTable II.

EXAMPLE XV

The procedure of Example XIV is repeated with the exceptions that noenzyme is added to the intermediate reactor, thereby, providing acontrol experiment. Ink removal results are presented in Table II.

EXAMPLE XVI

The procedure of Example I is repeated with the exceptions that theintermediate reactor and float cell volumes are increased to 4 liter and12 liter respectively, that 0.05% Alkamide® C-5 is used in theintermediate reactor and float steps and that sampling points are at 0.5minute intervals during flotation and that only ink removal by dirtcount measurement is assessed. Ink removal results are presented inTable II.

EXAMPLE XVII

The procedure of Example XVI is repeated with the exception that noenzyme is added to the intermediate reactor, thereby, providing acontrol experiment. Ink removal results are presented in Table II.

                                      TABLE II                                    __________________________________________________________________________              Ink Removal (%)                                                     Flotation Time (min)                                                                    Example XII                                                                          Example XIII                                                                         Example XIV                                                                          Example XV                                                                           Example XVI                                                                          Example XVII                     __________________________________________________________________________    0.5       58.3   54.8   47.8   50.6   48.9   46.7                             1.0       78.7   70.1   71.8   67.9   63.3   69.3                             1.5       83.0   79.6   83.8   82.1   77.9   76.1                             2.0       91.0   87.9   89.6   88.5   85.8   82.0                             2.5       94.0   92.1   91.8   89.8   87.6   84.7                             __________________________________________________________________________

EXAMPLE XVIII

The procedure of Example I is repeated with the exceptions that theintermediate reactor and float cell volumes are increased to 4 liter and12 liter respectively, that 0.03% Rhodasurf® BC720 is used in theintermediate reactor and float steps and that sampling points are at 0.5minute intervals during flotation and that only ink removal by dirtcount measurement is assessed. Ink removal results are presented inTable III.

EXAMPLE XIX

The procedure of Example XVIII is repeated with the exception that noenzyme is added to the intermediate reactor, thereby, providing acontrol experiment. Ink removal results are presented in Table III.

EXAMPLE XX

The procedure of Example I is repeated with the exceptions that theintermediate reactor and float cell volumes are increased to 4 liter and12 liter respectively, that 0.2% and 0.055% Hipochem® DI-600 is used inthe intermediate reactor and float steps respectively and that samplingpoints are at 0.5 minute intervals during flotation and that only inkremoval by dirt count measurement is assessed. Ink removal results arepresented in Table Ill.

EXAMPLE XXI

The procedure of Example XX is repeated with the exception that noenzyme is added to the intermediate reactor, thereby, providing acontrol experiment. Ink removal results are presented in Table Ill.

EXAMPLE XXII

The procedure of Example I is repeated with the exceptions that theintermediate reactor and float cell volumes are increased to 4 liter and12 liter respectively, that 0.05% and 0.055% Antarox® LA-EP-16 is usedin the intermediate reactor and float steps respectively and thatsampling points are at 0.5 minute intervals during flotation and thatonly ink removal by dirt count measurement is assessed. Ink removalresults are presented in Table III.

EXAMPLE XXIII

The procedure of Example XXII is repeated with the exception that noenzyme is added to the intermediate reactor, thereby, providing acontrol experiment. Ink removal results are presented in Table III.

                                      TABLE III                                   __________________________________________________________________________              Ink Removal (%)                                                     Flotation Time (min)                                                                    Example XVIII                                                                        Example XIX                                                                          Example XX                                                                           Example XXI                                                                          Example XXII                                                                         Example XXIII                    __________________________________________________________________________    0.5       56.8   48.9   74.8   68.1   56.9   53.1                             1.0       76.7   68.6   78.8   70.5   67.1   71.9                             1.5       84.9   83.2   77.7   68.7   77.5   74.9                             2.0       90.4   89.4   75.8   65.1   82.4   77.7                             2.5       94.4   92.2   75.3   65.9   84.3   80.9                             __________________________________________________________________________

The preferred embodiments have been described in detail herein above forthe purpose of illustration only, It will be apparent to a practitionerof ordinary skill in the art that various modifications could be made tothe above described examples without departing from the spirit and scopeof the invention as defined in the claims set forth hereinafter.

What is claimed is:
 1. A method for deinking office wastepapercomprising the steps of:a) converting office wastepaper paperscomprising a majority of xerographically printed or laser printed paperto a pulp slurry containing ink particles, wherein the ink particleshave large, plate-like structures which are too large to be removed bywashing or flotation and too flat to be removed by screens and cleaners;b) contacting the pulp slurry with a deinking agent consistingessentially of:i) an enzyme active at a pH of from about 4 to about 9;and ii) a nonionic surfactant selected from the group consisting ofa) afatty alcohol having a carbon number of from about 8 to about 22,alkoxylated with ethylene oxide and propylene oxide, as represented byformula (I)

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H;(I)

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22, x represents the number ofoxyethylene groups per molecule and is in the range of from about 3 toabout 25, and y represents the number of oxypropylene groups permolecule and is in the range of from about 1 to about 10; b) a fattyalcohol having a carbon number of from about 8 to about 22, alkoxylatedwith ethylene oxide and propylene oxide, as represented by formula (II):

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3).sub.y --(CH.sub.2 CH.sub.2 O).sub.x' --(CH.sub.2 CH(CH.sub.3)--O).sub.y' --H;(II)

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22, x and x', which may the same ordifferent represents the number of oxyethylene groups per molecule andis in the range of from about 2 to about 25, and y represents the numberof oxypropylene groups per molecule and is in the range of from 0 toabout 10; c) a fatty acid having a carbon number of from about 12 toabout 18, alkoxylated with ethylene oxide and propylene oxide, asrepresented by formula (Ill):

    R--C(O)O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H;                                                      (III)

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 12 to about 18, x represents the number ofoxyethylene groups per molecule and is in the range of from about 3 toabout 25, and y represents the number of oxypropylene groups permolecule and is in the range of from about 2 to about 15; and d) anethoxylated fatty alcohol of formula (X):

    RO(CH.sub.2 CH.sub.2 O).sub.x --H                          (X)

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 12 to about 18 and x represents the number ofoxyethylene groups per molecule and is in the range of from about 5 toabout 15 in an aqueous medium having a pH of from about 4 to about 9;and c) removing the ink particles from the pulp slurry of step (b) byflotation or a combination of flotation and water washing;wherein theparticle size of the ink particles on the office wastepaper papers priorto step (b) is reduced during step (b) to a size wherein the inkparticles can be removed in step (c).
 2. The method according to claim 1wherein the enzyme is active at a pH of from about 4 to about
 8. 3. Themethod according to claim 2 wherein the nonionic surfactant isrepresented by formula (I) wherein R is a straight-chain or branchedalkyl group having a carbon number of from about 8 to about 14, xrepresents the number of oxyethylene groups per molecule and is in therange of from about 3 to about 12, and y represents the number ofoxypropylene groups per molecule and is in the range of from about 1 toabout
 6. 4. The method according to claim 1 wherein the enzyme is acellulase.
 5. A method for deinking office wastepaper comprising thesteps of:a) converting wastepaper papers comprising a majority ofxerographically printed or laser printed paper to a pulp in an aqueousmedium to form a pulp slurry containing ink particles, wherein the inkparticles have large, plate-like structures which are too large to beremoved by washing or flotation and too flat to be removed by screensand cleaners, said aqueous medium comprising a deinking agent consistingessentially of:i) an enzyme active at a pH of from about 4 to about 9;and ii) a nonionic surfactant selected from the group consisting ofa) afatty alcohol having a carbon number of from about 8 to about 22,alkoxylated with ethylene oxide and propylene oxide, as represented byformula (I)

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H(I);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22, x represents the number ofoxyethylene groups per molecule and is in the range of from about 3 toabout 25, and y represents the number of oxypropylene groups permolecule and is in the range of from about 1 to about 10; b) a fattyalcohol having a carbon number of from about 8 to about 22, alkoxylatedwith ethylene oxide and propylene oxide, as represented by formula (II):

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --(CH.sub.2 CH.sub.2 O).sub.x' --(CH.sub.2 CH(CH.sub.3)--O).sub.y' --H(II);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22, x and x', which may the same ordifferent represents the number of oxyethylene groups per molecule andis in the range of from about 2 to about 25, and y represents the numberof oxypropylene groups per molecule and is in the range of from 0 toabout 10; c) a fatty acid having a carbon number of from about 12 toabout 18, alkoxylated with ethylene oxide and propylene oxide, asrepresented by formula (III):

    R--C(O)O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H(III);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 12 to about 18, x represents the number ofoxyethylene groups per molecule and is in the range of from about 3 toabout 25, and y represents the number of oxypropylene groups permolecule and is in the range of from about 2 to about 15; and d) anethoxylated fatty alcohol of formula (X):

    RO(CH.sub.2 CH.sub.2 O).sub.x --H                          (X)

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 12 to about 18 and x represents the number ofoxyethylene groups per molecule and is in the range of from about 5 toabout 15; wherein the pH of the aqueous medium is from about 4 to about9; and b) removing the ink particles from the pulp slurry of step (a) byflotation or a combination of flotation and water washing;wherein theparticle size of the ink particles on the office wastepaper papers priorto step (a) is reduced during step (a) to a size wherein the inkparticles can be removed in step (b).
 6. The method according to claim 5wherein the enzyme is active at a pH of from about 4 to about 8 and is acellulase.
 7. The method according to claim 5 wherein the nonionicsurfactant is of formula (I) wherein R is a straight-chain or branchedalkyl group having a carbon number of from about 8 to about 14, xrepresents the number of oxyethylene groups per molecule and is in therange of from about 3 to about 12, and y represents the number ofoxypropylene groups per molecule and is in the range of from about 1 toabout
 6. 8. A method for deinking office wastepaper comprising the stepsof:a) converting the office wastepaper papers comprising a majority ofxerographically printed or laser printed paper to a pulp in water toform a pulp slurry containing ink particles, wherein the ink particleshave large, plate-like structures which are too large to be removed bywashing or flotation and too flat to be removed by screens and cleaners,wherein the pulp slurry consists essentially of from about 10% to about14% on a dry weight basis pulp; b) diluting the pulp slurry of step (a)with water until the pulp slurry consists essentially of from about 1%to about 6% on a dry weight basis pulp; c) contacting the pulp slurry ofstep (b) for a sufficient amount of time with a sufficient amount ofdeinking agent consisting essentially of:i) an enzyme active at a pH offrom about 4 to about 9; and ii) a nonionic surfactant selected from thegroup consisting ofa) a fatty alcohol having a carbon number of fromabout 8 to about 22, alkoxylated with ethylene oxide and propyleneoxide, as represented by formula (I)

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H(I);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22, x represents the number ofoxyethylene groups per molecule and is in the range of from about 3 toabout 25, and y represents the number of oxypropylene groups permolecule and is in the range of from about 1 to about 10; b) a fattyalcohol having a carbon number of from about 8 to about 22, alkoxylatedwith ethylene oxide and propylene oxide, as represented by formula (II):

    R--O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --(CH.sub.2 CH.sub.2 O).sub.x' --(CH.sub.2 CH(CH.sub.3)--O).sub.y' --H(II);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 8 to about 22, x and x', which may the same ordifferent represents the number of oxyethylene groups per molecule andis in the range of from about 2 to about 25, and y represents the numberof oxypropylene groups per molecule and is in the range of from 0 toabout 10; c) a fatty acid having a carbon number of from about 12 toabout 18, alkoxylated with ethylene oxide and propylene oxide, asrepresented by formula (III):

    R--C(O)O--(CH.sub.2 CH.sub.2 O).sub.x --(CH.sub.2 CH(CH.sub.3)--O).sub.y --H(III);

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 12 to about 18, x represents the number ofoxyethylene groups per molecule and is in the range of from about 3 toabout 25, and y represents the number of oxypropylene groups permolecule and is in the range of from about 2 to about 15; and d) anethoxylated fatty alcohol of formula (X):

    RO(CH.sub.2 CH.sub.2 O).sub.x --H                          (X)

wherein R is a straight-chain or branched alkyl group having a carbonnumber of from about 12 to about 18 and x represents the number ofoxyethylene groups per molecule and is in the range of from about 5 toabout 15; wherein said aqueous medium has a pH of from about 4 to about9 and a temperature consistent with the optimal activity of the enzyme;d) adjusting the pH or temperature of the pulp slurry of step (c) todenature the enzyme; and e) removing the ink particles from the pulpslurry of step (d) by flotation or a combination of flotation and waterwashing;wherein the particle size of the ink particles on the officewastepaper papers prior to step (c) is reduced during step (c) to a sizewherein the ink particles can be removed in step (e).
 9. The methodaccording to claim 8 wherein the enzyme is active at a pH of from about4 to about
 8. 10. The method according to claim 8 wherein the nonionicsurfactant is of formula (I) wherein R is a straight-chain or branchedalkyl group having a carbon number of from about 8 to about 14, xrepresents the number of oxyethylene groups per molecule and is in therange of from about 3 to about 12 and y represents the number ofoxypropylene groups per molecule and is in the range of from about 1 toabout
 6. 11. The method according to claim 8 wherein the enzyme is acellulase.
 12. The method according to claim 8 wherein the aqueousmedium of the contacting step has a temperature of from about 40° C. toabout 65° C. and the deinking agent remains in contact with the aqueousmedium for from about 5 minutes to about 90 minutes.